Adjustable beds are well known, and are used in a variety of applications including for medical or domestic use. Such adjustable beds are often used by people having limited mobility, be it as a result of being obese, having a medical condition, or otherwise. Adjustable beds are often used in hospitals and other medical care facilities, however a growing number of obese and other mobility challenged people are using adjustable beds domestically to improve their quality of life. Adjustable beds are typically articulated in at least one location, and enable the orientation and vertical elevation of the sleep surface to be modified as required.
“Low-profile” adjustable beds, namely beds which allow the sleeping surface to be positioned very close to the ground when the bed is disposed in its fully collapsed or fully lowered position, are becoming increasing popular. There are several advantages associated with being able to collapse a bed to such a low-profile position, the primary among which is that they make the process of getting onto and off the bed much easier for the user/patient. Another advantage of low-profile beds, particularly useful for hospital patients which are at risk of falling out of a hospital bed, is that they enable the sleeping surface to be positioned as close to the ground as possible.
However, these low-profile beds must still be able to be adjusted such that they can be raised to a much higher position so that medical staff have comfortable access to the patient. Due to the mechanisms required to permit the movement of the bed and the motors required to actuate such mechanisms, such known low-profile beds do not normally allow a fully-collapsed position of less than about 8 inches above the ground surface. Additionally, another disadvantage of known low-profile beds is that the typical configurations of the lifting mechanisms of a very low-profile bed typically place the actuators for raising and lowering the bed at a very shallow angle when the bed is in the fully lowered/collapsed position. Accordingly the actuators, which are already limited somewhat in lifting capacity by their small size required for them to fit within the tight space envelope of such a low-profile bed structure, can only produce a small vertical force component due to the relatively shallow angle at which the actuator is positioned beneath the bed. As such, this small vertical force component can significantly limit, if not completely prevent, the ability to lift the bed and patient.
In the past, these drawbacks have limited the minimum height of mechanically actuated adjustable beds as well as their maximum lift capacity (ex: maximum weight of patient). For example, for the reasons set out above, most existing low-profile beds which permit a minimum vertical height (i.e. in the fully-lowered position) of 8 inches or less, have a maximum lift capacity of 500 lbs. Accordingly, these low-profile beds become unsuitable for obese patients/users weighing more than 500 lbs. As a means for comparison, adjustable beds of the type specifically designed for obese patients typically have a maximum lift capacity of 1000 lbs, however these obese-specific beds cannot be lowered into a low profile position. Attempts to design a bed which reaches a compromise between lift capacity and minimum fully-lowered height have been attempted, however such beds typically only permit a height adjustment range of 9.5 to 29 inches at a maximum load of 850 lbs (i.e. they only permit a minimum elevation of 9.5 inches when disposed in the fully-lowered position, and can only support a patient of less than 850 lbs). Thus, such beds either cannot be collapsed into a real low-profile position (ex: less than 9.5 inches) due to the larger actuators and mechanism geometry which permit a higher lift capacity, or have limited lift capacity.
Attempts to address the above-mentioned issues have been made. U.S. Pat. No. 6,473,922 issued Nov. 5, 2002 to Sommerfeld et al. discloses, for example, an articulated bed which attempt to minimize the amount of force required to raise the bed from its lowered position. However, several disadvantages exist with this articulated bed structure. The bed taught by Sommerfeld includes a main frame, on which the sleep surface platform is mounted, and which is supported by a pair of pivoting legs. The legs are supported and actuated by stabilizers, and have wheels on the outer free ends thereof. Accordingly, in order for the sleep surface to be vertically raised or lowered, the pivoting legs must swing through their travel arc, as shown in FIG. 2 for example. This results in vertical displacement of the entire bed structure. As can be seen in FIG. 2 of Sommerfeld, for example, if the longitudinal position of the end of a first one of the pivoting legs (such as the one closest to the headboard for example) is kept stationary, then actuating the bed to raise or lower the sleep surface will cause the opposite second leg to move longitudinally outward as the leg pivots through its radius of travel. This accordingly causes a longitudinal displacement of the entire bed, in this case in a direction towards the foot of the bed. Clearly, such lateral translation of the entire bed during height adjustment is undesirable. Other disadvantages with the bed described in U.S. Pat. No. 6,473,922 also exist. For example, this configuration requires the bed to be moved into its fully collapsed/lowered position, as shown in FIG. 1 for example, before the entire bed can be displaced on the floor. Once in the fully lowered position, the caster wheels mounted on the main frame engage the floor, thereby permitting displacement of the bed as needed, for example to move the bed from one hospital room to another. When the bed is in an extended position, whereby the sleep surface is raised away from the fully collapsed position, the bed is not displaceable. Clearly, this is undesirable, particularly in hospital and other medical applications.
Sommerfeld's articulated bed structure is of the type without a fixed base. Fixed base beds are often preferred because they eliminate any possibility that the bed is laterally displaced (either longitudinally (forward-backward), or laterally (sideways)) during the vertical height adjustment of the sleep surface. However, fixed base bed designs have, in the past, been incompatible with permitting a very low minimum height—i.e. existing fixed base bed designs have not been able to accommodate the desired low-profile minimum height position, because the fixed base alone is often higher than the desired minimum sleep surface height of 8 inches or less, and therefore the overall minimum height of such beds is often over 12 inches in the fully collapsed position. This is considered undesirable for applications in which a low-profile bed is desired or required.
There therefore remains a need for an improved adjustable bed or other adjustable platform, particularly one having a high lift capacity while minimizing the elevation of the bed when fully lowered.